From 1f658ff72921207392e512df2fbe8cea66b5ceb7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Va=CC=81clav=20Slavi=CC=81k?= <vaclav@slavik.io>
Date: Tue, 13 Feb 2024 13:38:37 +0100
Subject: [PATCH] Override GetPreferredUILanguages with WXLANGUAGE

Add support for overriding GetPreferredUILanguages() return value by
setting the WXLANGUAGE environment variable to a colon-separated list
of desired languages (same as GNU's LANGUAGE variable).

Primarily used for unit tests, but may be more generally useful.
---
 docs/doxygen/overviews/envvars.h |  6 ++++++
 src/common/uilocale.cpp          | 30 +++++++++++++++++++++++++++++-
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/docs/doxygen/overviews/envvars.h b/docs/doxygen/overviews/envvars.h
index 7b6386d8e4..21079cc25a 100644
--- a/docs/doxygen/overviews/envvars.h
+++ b/docs/doxygen/overviews/envvars.h
@@ -51,6 +51,12 @@ wxWidgets programs.
          default value if it's not a number, so that e.g. setting it to "yes"
          suppresses all GTK diagnostics while setting it to 16 only suppresses
          GTK warning messages.}
+@itemdef{WXLANGUAGE,
+         This variable can be set to override OS setting of preferred languages
+         and make wxUILocale::GetPreferredUILanguages() return the set list
+         instead. The format is same as GNU's <a
+         href="https://www.gnu.org/software/gettext/manual/html_node/The-LANGUAGE-variable.html">LANGUAGE</a>
+         variable: a colon-separated list of language codes.}
 */
 
 @see wxSystemOptions
diff --git a/src/common/uilocale.cpp b/src/common/uilocale.cpp
index 014d32b678..e52fa2d833 100644
--- a/src/common/uilocale.cpp
+++ b/src/common/uilocale.cpp
@@ -24,6 +24,9 @@
 
 #include "wx/arrstr.h"
 #include "wx/intl.h"
+#include "wx/log.h"
+#include "wx/tokenzr.h"
+#include "wx/utils.h"
 
 #ifndef __WINDOWS__
     #include "wx/language.h"
@@ -31,6 +34,8 @@
 
 #include "wx/private/uilocale.h"
 
+#define TRACE_I18N wxS("i18n")
+
 // ----------------------------------------------------------------------------
 // helper functions
 // ----------------------------------------------------------------------------
@@ -678,7 +683,7 @@ int wxUILocale::GetSystemLanguage()
 {
     const wxLanguageInfos& languagesDB = wxGetLanguageInfos();
     size_t count = languagesDB.size();
-    wxVector<wxString> preferred = wxUILocaleImpl::GetPreferredUILanguages();
+    wxVector<wxString> preferred = wxUILocale::GetPreferredUILanguages();
 
     for (wxVector<wxString>::const_iterator j = preferred.begin();
         j != preferred.end();
@@ -743,6 +748,29 @@ int wxUILocale::GetSystemLocale()
 /* static */
 wxVector<wxString> wxUILocale::GetPreferredUILanguages()
 {
+    // The WXLANGUAGE variable may contain a colon separated list of language
+    // codes in the order of preference. It is modelled after GNU's LANGUAGE:
+    // http://www.gnu.org/software/gettext/manual/html_node/The-LANGUAGE-variable.html
+    wxString languageFromEnv;
+    if (wxGetEnv("WXLANGUAGE", &languageFromEnv) && !languageFromEnv.empty())
+    {
+        wxVector<wxString> preferred;
+        wxStringTokenizer tknzr(languageFromEnv, ":");
+        while (tknzr.HasMoreTokens())
+        {
+            const wxString tok = tknzr.GetNextToken();
+            if (const wxLanguageInfo* li = wxUILocale::FindLanguageInfo(tok))
+            {
+                preferred.push_back(li->CanonicalName);
+            }
+        }
+        if (!preferred.empty())
+        {
+            wxLogTrace(TRACE_I18N, " - using languages override from WXLANGUAGE: '%s'", languageFromEnv);
+            return preferred;
+        }
+    }
+
     return wxUILocaleImpl::GetPreferredUILanguages();
 }